In the automotive industry, there continues to be an effort to create vehicles having aesthetically pleasing exterior and interior designs. The importance of appearance and aesthetic appeal in the automotive interior continues to grow. In particular, attractive upholstered coverings for interior trim, seats, ornamental roof caps and steering wheels aid in selling the modern, high-quality automobile. Customer quality demands continue to raise the bar for potential owner acceptability, and aesthetic appeal has become a critical factor in the marketing of higher profit margin vehicles. One example of such improved aesthetics involves the appearance of seams in upholstered interior and exterior components. In addition, methods of reducing manufacturing costs involved with trim components continue to be needed.
Seams in coverstocks for interior and exterior automotive components may be included simply to break up a broad expanse of material, to accentuate styling lines, to connect different materials together, to allow conformability of the stock to curved surfaces (as in seating) and in the case where the complexity of the curved surface being covered cannot be accomplished with a single sheet of material.
One type of prior art seam that is used on many automotive vehicle interior components, including seats, is a French seam that presents a neat appearance for a joint which joins two pieces of material together at a secured seam. Prior art French seams have been made by applying a foam material to the back side of the leather, vinyl or other types of coverstock to ensure that the foam is secured to the coverstock. One portion of a first material may then be sewn to a portion of a second material. Then the edges may then be flipped over each other and stitches placed a predetermined distance from the joint seam to create a French seam look. The French seam gets the appearance from the foam being compressed on itself creating a hump-like appearance adjacent to the seam thus creating the look that is desired by many automobile designers.
Welts are originally known from the upholstery industry and are generally a rod-shaped element that is bonded, welded or stitched to the coverstock of the upholstery. The welt may be attached along the edges of the upholstery and may be used to position the coverstock in accordance with the shape of the underlying cushion. Conventional welts may comprise a flexible welt core sheathed in a covering material and a laterally protruding welt flap. The sheathing may comprise cut strips of covering material which may be placed around the welt core and bonded or stitched at the ends. The welts produced in this way may then be stitched onto the edges of the sown material.
In addition, welts have been used in the automobile industry, particularly on seats, head rests and arm rests. These welts are mainly used for covering otherwise visible joints between two sheets of material and may be integrally formed by folding the coverstock and creating a standard deck seam as is shown in FIG. 7. In this way, these welts embellish the aesthetic appearance of the automobile interior.